The　high-speed　flow　of　fuel　in　the　injector　of　the　high　pressure　fuel　system　for　the　diesel　engine　is　easy　to　induce　the　cavitation　in　nozzles,　which　affects　the　injection　characteristics.　A　set　of　test　rigs　is　built　to　adjust　the　different　outlet　pressures　for　the　study　of　the　influence　of　outlet　pressure　on　the　discharge　characteristics　of　injector.　The　injection　characteristics　of　a　high-pressure　common-rail　under　different　injection　and　outlet　pressures　are　measured　to　investigate　the　influence　of　outlet　pressure　on　fuel　delivery　rate.　The　test　results　show　that　the　outlet　pressure　has　little　influence　on　the　fuel　delivery　rate　at　the　constant　injection　pressure;　but　as　the　flow　chokes　due　to　cavitation,　the　discharge　coefficient　increases　with　the　increase　in　the　outlet　pressure.　©,　2015,　China　Ordnance　Society.　All　right　reserved.